Rotary devices such as rotary dryers, drums, trommels and tumblers, for example, are well known in industry. Such devices are used for drying, mixing, separating, or milling of different materials such as ores, fibers, or vegetative materials such as tobacco. (A trommel is a revolving cylindrical sieve used for screening or sizing rock or other particulate into different size groups.) These units typically include a long cylinder which is positioned with the axis lying horizontally or slightly tilted to cause loose material within to migrate from the input end to the output end of the cylinder. Both ends of the cylinder are typically open. The cylinder is caused to spin on an axis and preferably has shallow spiraling fins or a similar structure attached to the inner wall of the cylinder, resembling internal threads, for the movement of loose material from the higher input end to and out of the lower discharge end. Due to the use of internal spiraling ribs or fins, the axis of drum rotation is perfectly or nearly level in some configurations.
The material to be processed is added into the higher end. As the cylinder spins, the material is carried upward within and against the walls and internal spiral ribs or fins and drops back to the bottom of the cylinder, but due to the configuration of the spiraling fins and the slight tilt of the cylinder, the material falls ever closer to the lower end of the cylinder. In a drying drum, while the material is dropping toward the lower end, drying air, steam or the like, is passed through the cylinder to dry the process material dropping and passing through the drum. In a ball mill, heavy, hardened balls drop along with the process material to be milled, such that as the balls fall on and against the process material, the process material is crushed or pulverized. In a mixing drum, differing ingredients are added simultaneously to the input end of the drum and these are uniformly mixed as they exit the lower end of the drum.
The preceding discussion describes a continuous flow process. However, instead of a process wherein material is continuously added into the input of the cylinder and finished product continuously falls out of the output end, a ‘batch’ processing unit is also possible. Such a unit has is preferably a closed cylinder with at least one door which is opened to put material in the cylinder. The material is processed and then the door or doors are opened to remove the processed material.
Rotary drums vary from a few feet in length and diameter to over a hundred feet in length and tens of feet in diameter. These drums can weigh from a few hundred pounds to tens or hundreds of tons. A common problem with such drums is the means of support on which the drums spin. Typically, the drums are supported by wheels or rollers configured within semi-circular cradles which allow the drums to spin. The rollers contact the drum on strengthened and hardened annular external rings on the outer walls of the drum. Additionally, in some cylinders, an axle with some type of bearings may support or help to support a spinning cylinder.
In many industrial environments, the materials to be processed are abrasive and through contamination and abrasion, cause failure of the roller surfaces and the bearings in the rollers. Larger and heavier drums require larger and heavier rollers with larger and heavier bearings. When bearings or rollers fail, the rotary drum must be emptied and shut down to repair or replaced the failed part. When such failures occur, expensive parts must be replace. Further, downtime causes significant expense as well. Another expensive characteristic of such industrial cylinders is that mechanical bearings need lubrication which may also inadvertently contaminate process material.
Conventional rotary drum dryer (usually a large cylinder having steam coils inside) supported on bearings held in cradles. Particular matter such as grain or other granular material is tumbled from one end of the dryer to the other to dry or mix the particles. These dryers can weight tons and take large electric motors to turn.
The present invention utilizes a plurality of permanent magnets affixed around the outside diameter of the drum dryer at selected locations. A cradle having permanent magnets of a reverse polarity support the dryer. The dryer is supported and suspended above the magnets mounted in the cradle eliminating any frictional drag or bearings. The axial ends of the drum dryer include a metal cap or pole in magnetic engagement with a magnet extending from a support.
The drum dryer can be rotated by conventional electric motor and gear or belt means; however a preferred embodiment uses a plurality of magnets extending from a wheel mounted to a electric motor shaft which are in magnetic communication with a plurality of magnets mounted to and extending from the periphery of the distal end of the drum at selected spacing so that rotation of the motor turns the motor magnets magnetically coupled to the drive magnets mounted on the end of the dryer to rotate same.